Advanced Subnet Validator Calculator

Calculator Inputs

Primary IPv4 Address

Subnet Mask

CIDR Prefix

Comparison IP

Gateway IP

Required Hosts

Reserved Hosts

Network Label

Example Data Table

IP Address	Subnet Mask	CIDR	Network Address	Broadcast Address	Usable Hosts	Status
192.168.10.34	255.255.255.0	/24	192.168.10.0	192.168.10.255	254	Valid usable host
10.20.15.200	255.255.248.0	/21	10.20.8.0	10.20.15.255	2046	Valid usable host
172.16.5.0	255.255.255.0	/24	172.16.5.0	172.16.5.255	254	Network address, not host

Formula Used

Network Address = IP Address AND Subnet Mask

Wildcard Mask = 255.255.255.255 minus Subnet Mask

Broadcast Address = Network Address OR Wildcard Mask

Total Addresses = 2^{(32 - prefix)}

Usable Hosts = Total Addresses minus 2 for most subnets

Special Cases: /31 provides two point-to-point endpoints. /32 represents one exact host route.

How to Use This Calculator

Enter the primary IPv4 address you want to inspect.
Provide a subnet mask, CIDR prefix, or both.
Add an optional comparison IP to test subnet membership.
Add an optional gateway IP to verify usability.
Enter required and reserved host counts for planning.
Press Validate Subnet to display results above the form.
Use the export buttons to save the summary as CSV or PDF.

Frequently Asked Questions

1) What does a subnet validator check?

It checks whether an IPv4 address, subnet mask, and prefix create a valid subnet. It also calculates network address, broadcast address, usable range, host capacity, and related planning details.

2) Can I enter both mask and CIDR?

Yes. When both values are entered, the calculator compares them. If they do not represent the same subnet size, the tool shows an error so you can correct the mismatch.

3) Why can an address be invalid as a host?

An address may be the network address or the broadcast address. In most IPv4 subnets, those two values are reserved and cannot be assigned to regular devices.

4) What is the wildcard mask used for?

A wildcard mask is the inverse of the subnet mask. It is useful in routing, firewall logic, and access control entries where matching flexible address ranges matters.

5) How does the comparison IP feature help?

It tests whether another IPv4 address falls inside the same subnet. That helps confirm host grouping, device placement, VLAN assignments, or peer reachability before deployment.

6) Why are /31 and /32 handled differently?

A /31 is commonly used for point-to-point links, where both addresses may be usable. A /32 does not describe a network range. It identifies one exact host route.

7) Can this calculator help with capacity planning?

Yes. Enter required hosts and reserved hosts to compare subnet capacity against demand. The result shows remaining usable space and whether the subnet can support the requested count.

8) Does this tool support IPv6?

No. This version is designed for IPv4 subnet validation only. The logic, formatting, and host calculations here are specific to 32-bit IPv4 addressing.